JP2010145917A - Image projection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact image projection apparatus of high performance which can expansively project a bright image on the plane of projection at a wide image angle, even with a large aperture ratio. <P>SOLUTION: If the cone angle of illumination light reflected by a DMD (digital micro mirror device) is not more than the cone angle of an projection optical system, the F number of the projection optical system is defined as Fno, the angle between the main light of the illumination light reflected by the DMD and the optical axis of the projection optical system is defined as α, and the cone angle of the illumination light reflected by the DMD is defined as β, relations Fno<1.8, 8.5°<α<10.5° and β<11.5° are satisfied; and if the exit pupil position of the projection optical system is defined as EXP, the angle formed between the normal obtained by connecting the exit pupil center of the projection optical system and the maximum image height of the DMD and the optical axis of the projection optical system is defined as θ<SB>1</SB>; the angle formed between the lower light at the maximum image height of the projection optical system and the optical axis of the projection optical system is defined as θ<SB>2</SB>and the angle formed between the lower light of the illumination light reflected by the DMD and the optical axis of the projection optical system is defined as θ<SB>3</SB>, relations θ<SB>1</SB>=θ<SB>2</SB>-sin(1/(Fno×2)), θ<SB>2</SB>>β-θ<SB>3</SB>and 41 mm<EXP<60 mm are satisfied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image projection apparatus that enlarges and projects an image formed by a reflective spatial light modulator on a projection surface.

  Projectors that are image projection apparatuses include a liquid crystal system and a DLP (Digital Light Processing: registered trademark) system. Among these, the DLP system uses a reflective spatial light modulation element called DMD (Digital Micromirror Device: registered trademark).

  DMD is formed by arranging a number of micromirrors on the CMOS semiconductor device that can change the tilt within the angle range of ± 12 ° around the torsion axis using MEMS (Micro Electro Mechanical Systems) technology. The direction of reflection of light from the light source is controlled while switching the inclination of each mirror in accordance with the image signal, and an image can be displayed depending on the presence or absence (ON / OFF) of reflected light from each mirror.

  In addition, the DLP projector has an illumination optical system that makes the illumination light condensed on the DMD incident thereon and an image formed by the illumination light reflected by the DMD on a projection surface such as a screen. A projection optical system that performs enlarged projection (see, for example, Patent Documents 1 to 5).

  Here, in a DLP projector, for example, when the illumination optical system is a telecentric optical system and the projection optical system is a telecentric optical system, it is necessary to arrange a field lens or the like on the front surface of the DMD, and a larger lens. Because of the caliber, these are factors that increase costs. In order to reduce the size and thickness of the projector, a more compact projector with a small lens diameter is required.

  On the other hand, when the illumination optical system is a telecentric optical system and the projection optical system is a non-telecentric optical system, a field lens is not required, but it is not affected by the illumination optical system that makes illumination light incident on the DMD. In order to achieve this, it is necessary to lengthen the back focus to some extent. However, the longer the back focus, the more difficult the lens design for obtaining good optical performance. For example, depending on the incident angle of the illumination light from the illumination optical system to the DMD, part of the peripheral light beam incident from the lens end of the projection optical system out of the effective aperture of the projection optical system out of the illumination light reflected by the DMD As a result, it may not be received at the lens end, and as a result, the peripheral light amount may be reduced.

JP 2003-185964 A JP 2008-107844 A JP 2000-98272 A Japanese Patent Laid-Open No. 11-249069 JP 2008-146085 A

  The present invention has been proposed in view of the above-described conventional circumstances. In the combination of a telecentric illumination optical system and a non-telecentric projection optical system, the present invention is bright even with high performance, compactness, and a large aperture ratio. An object of the present invention is to provide an image projection apparatus capable of enlarging and projecting an image on a projection surface with a wide angle of view.

In order to achieve the above object, an image projection apparatus according to the present invention includes a light source, a telecentric illumination optical system that collects light emitted from the light source to form illumination light, and modulates and reflects the illumination light. A reflection-type spatial light modulation element that forms an image according to the image signal, and a non-telecentric projection optical system that enlarges and projects the image on the projection surface, and the illumination light reflected by the spatial modulation element The cone angle is less than or equal to the cone angle of the projection optical system, the F number of the projection optical system is Fno, the angle between the chief ray of illumination light reflected by the spatial modulation element and the optical axis of the projection optical system is α, spatial modulation When the cone angle of the illumination light reflected by the element is β, the relationship of Fno <1.8, 8.5 ° <α <10.5 °, β <11.5 ° is satisfied, and the projection optical system EXP is the exit pupil position of the projection optical system Angle of theta ₁ between the optical axis and the center of the space the maximum image height and the connecting's better line projection optical system of the modulation _device, the optical axis of the lower ray and the projection optical system at the maximum image height of the projection optical system Θ ₁ = θ ₂ −sin (1 / (Fno ×), where θ _{2 is} the angle formed by θ ₂ and the angle between the lower ray of the illumination light reflected by the spatial light modulator and the optical axis of the projection optical system is θ _3. 2)), θ ₂ > β−θ ₃ , 41 mm <EXP <60 mm.

  In the image projection apparatus according to the present invention, when a telecentric illumination optical system and a non-telecentric projection optical system are combined, by satisfying the above relationship, among the illumination light reflected by the light modulation element, the projection optics It is possible to prevent a part of the peripheral light beam incident from the lens end of the system from deviating from the effective aperture of the projection optical system and cannot be received by the lens end, thereby improving the light utilization efficiency.

  As described above, according to the present invention, in a combination of a telecentric illumination optical system and a non-telecentric projection optical system, a high-performance and compact image with a large aperture ratio can be obtained on a projection surface with a wide angle of view. It is possible to provide an image projection apparatus capable of enlarging projection.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent. In addition, the lens data and the like exemplified in the following description is an example, and the present invention is not necessarily limited thereto, and can be appropriately modified and implemented without changing the gist thereof.

A DLP projector 50 shown in FIG. 1 will be described as an example of an image projection apparatus to which the present invention is applied.
As shown in FIG. 1, the projector 50 modulates and reflects the illumination light, a lamp 51 as a light source, an illumination optical system 52 that collects light emitted from the lamp 51 to form illumination light, and the illumination light. Thus, a DMD 53 that is a reflective spatial light modulation element that forms an image according to an image signal, and a projection optical system 54 that enlarges and projects the image on a screen 55 that is a projection surface are provided.

  Further, a color filter which is a rotary filter which is rotationally driven by arranging a color filter for separating light emitted from the lamp 51 into a plurality of color lights having different wavelengths between the lamp 51 and the illumination optical system 52 in the circumferential direction. A wheel 56 and a rod integrator 57 that is a light guide member that guides the color light that has passed through each filter of the color wheel 56 to the illumination optical system 52 are disposed.

  In the projector 50 to which the present invention is applied, the illumination optical system 52 is a telecentric optical system, the projection optical system 54 is a non-telecentric optical system, and does not use a field lens.

  Specifically, the illumination optical system 52 has a lens group having a positive refractive power as a whole, and the lenses L1 to L4 constituting the lens group are arranged in a state where their optical axes are aligned with each other. ing.

  On the other hand, the projection optical system 54 includes a first lens group 54a having a negative refractive power as a whole and a second lens group 54b having a positive refractive power as a whole. The lenses L5 to L14 constituting the two lens groups 54a and 54b are arranged in a state where the optical axes of the lenses are aligned. In addition, a diaphragm 56 is disposed between the lens L10 and the lens L11 constituting the second lens group 54b.

  The present invention is not necessarily limited to the lens configurations of the illumination optical system 52 and the projection optical system 54. For example, the shape of the lens, the combination thereof, the number of the lenses, and the like are within the scope of the present invention. It is possible to implement with appropriate changes.

  In the projector 50 to which the present invention is applied, the DMD 53 prevents the part of the peripheral light beam incident from the lens end of the projection optical system 54 from deviating from the effective aperture of the projection optical system 54 and cannot be received by the lens end. The cone angle of the reflected illumination light is equal to or less than the cone angle of the projection optical system 54.

  Here, the cone angle of the illumination light reflected by the DMD 53 is a spread angle of the illumination light reflected by the DMD 53 and incident on the projection optical system 54, and is a value represented by a full angle. On the other hand, the cone angle of the projection optical system 54 is an angle (referred to as an aperture angle) at which the exit pupil is stretched with respect to an image point on the optical axis of the projection optical system 54, and is generally a value represented by a half angle. . In the present invention, it means that the cone angle of the illumination light reflected by the DMD 53 is the same as or smaller than the cone angle of the projection optical system 54 when comparing each other in full angle (or half angle).

Further, in the projector 50 to which the present invention is applied, as shown in FIG. 2, the F-number of the projection optical system 54 is Fno, and the angle formed between the principal ray of the illumination light reflected by the DMD 53 and the optical axis of the projection optical system 54 Is preferably α and the cone angle of the illumination light reflected by the DMD 53 is β, it is preferable that the following relationship is satisfied.
Fno <1.8
8.5 ° <α <10.5 °
β <11.5 °
Fno is a value represented by the following equation.
Fno = 1 / (2sin (β + α))

  When Fno is smaller than 1.8, the projection optical system 54 cannot receive the lower light beam of the illumination light at the maximum image height in the lens configuration of the present invention. Similarly, when β is 11.5 ° or more, the projection optical system 54 cannot receive the light beam on the lower light side of the illumination light. The same applies when α is 8.5 ° or less. On the other hand, when α10.5 ° or more, the projection optical system 54 cannot receive the upper luminous flux of the illumination light at the center of the DMD 53.

  In the present invention, when the values of α and β satisfy the above relationship, the position of the exit pupil is important. This is because the angle received by the illumination light of the projection optical system 54 changes depending on the position of the exit pupil. For example, as shown in FIGS. 3A and 3B, the longer the exit pupil position, the more telecentric (the exit pupil position is ∞). 3A shows the case where the exit pupil position of the illumination optical system 52 is ∞ (telecentric), and FIG. 3B shows the case where the exit pupil position of the illumination optical system 52 is finite (non-telecentric). It is.

  In addition, when the exit pupil position of the illumination optical system 52 is sufficiently separated from the exit pupil position of the projection optical system 54, the difference in the angle of each lens beam is small, so that the light use efficiency is good. The projector 1 can be configured. On the other hand, when the exit pupil position of the projection optical system 54 becomes longer, the lens diameter becomes larger and it becomes difficult to reduce the size.

Therefore, in the projector 50 to which the present invention is applied, as shown in FIG. 4, the exit pupil position of the projection optical system 54 is EXP, and the exit pupil center of the projection optical system 54 and the maximum image height H _{1 of the} DMD 53 are connected. The angle formed by the elliptical line and the optical axis of the projection optical system is θ ₁ , the angle formed by the lower ray at the maximum image height H ₁ of the projection optical system and the optical axis of the projection optical system 54 is θ ₂ , and is reflected by the DMD 53. the angle between the optical axis of the have been lower ray of the illumination light projection optical system 54 when the theta _3, it is preferable to satisfy the following relation.
θ ₁ = θ ₂ −sin (1 / (Fno × 2))
θ ₂ > β−θ ₃
41mm <EXP <60mm
Note that EXP is a value represented by the following equation.
EXP = H ₁ / tan θ ₁

When EXP is 41 mm or less, the projection optical system 54 cannot receive the lower light beam of the illumination light at the maximum image height H ₁ . When EXP is 60 mm or more, the projection optical system 54 cannot receive the upper luminous flux of the illumination light at the center of the DMD 53.

  When the projection optical system 54 satisfies the above relationship and has an image height in which the upper side or the lower side of the DMD 53 coincides with the optical axis, the offset amount of the DMD 53 is preferably set to 100%. The offset amount referred to here is zero (0) when the optical axis of the projection optical system 54 is at the center of the DMD 53, and is positive when the optical axis of the projection optical system 54 is shifted to the upper side of the DMD 53 ( (+), And values shifted to the lower side of the DMD 53 as minus (−), respectively, in terms of 100% conversion. In general, the offset amount is normally + offset because the projector 1 is generally installed on a table and projects toward the upper screen 55 from the table. The offset amount can be changed as appropriate, and can be + 100% or more or + 100% or less depending on the size of the DMD 53.

In the projector 50 to which the present invention is applied, it is preferable that the following relationship is satisfied when the optical magnification of the illumination optical system is B.
B> 2.6
The optical magnification B is a value obtained by dividing the maximum emission angle of the illumination light after being emitted from the rod integrator 57 by β.

In the projector 50 to which the present invention is applied, it is preferable that the following relationship is satisfied when the back focus of the projection optical system 54 is BF in terms of air and the focal length is EFL.
BF> EFL × 0.9

  If the BF is too short, the illumination light that enters the DMD 53 from the illumination optical system 52 and the illumination light that is emitted (reflected) from the DMD to the projection optical system 54 intersect each other. is necessary. In the present invention, the above-described intersection of illumination lights is avoided by using the projection optical system 54 in which BF and EFL are substantially the same.

  Further, as shown in FIGS. 5A and 5B, the rod integrator 57 preferably has a cross-sectional shape in a direction orthogonal to its optical axis as a parallelogram. Specifically, when the rod integrator 57 has a rectangular cross-sectional shape as in the prior art, the illumination light condensed on the DMD 53 by the illumination optical system 52 is distorted as shown in FIG. Will result in a parallelogram.

  On the other hand, when the cross-sectional shape of the rod integrator 57 is a parallelogram as in the present invention, the illumination light condensed on the DMD 53 by the illumination optical system 52 is as shown in FIG. In addition, the distortion is corrected to be the same rectangle as DMD53. Thus, by performing aberration correction on the illumination optical system 52 side with the rod integrator 57, the lens configuration on the illumination optical system 52 side can be reduced in size at low cost.

  Furthermore, it is preferable that the rod integrator 57 has a shape in which an end surface 57a on the emission side is cut obliquely with respect to the optical axis. In this case, as shown in FIG. 7A, the illumination light is emitted obliquely from the end surface 57a on the emission side of the rod integrator 57, and is shown in the enclosed portion X in the figure by the so-called tilt effect. Thus, the illumination light collected on the DMD 53 via the illumination optical system 52 is focused on each light beam on the DMD 53. Thereby, the condensing characteristic of illumination light on DMD 53 can be further improved.

  On the other hand, as shown in FIG. 7B, when the end surface 57a on the emission side of the rod integrator 57 has a shape cut perpendicular to the optical axis, as shown in the encircled portion X in the figure, Since the focus of each light beam collected on the DMD 53 is deviated, the condensing characteristic of the illumination light on the DMD 53 is inferior to the case shown in FIG.

  As described above, in the projector 1 to which the present invention is applied, when the telecentric illumination optical system 52 and the non-telecentric projection optical system 54 are combined, the illumination light reflected by the DMD 53 is satisfied by satisfying the above relationship. Among them, it is possible to prevent a part of the peripheral luminous flux incident from the lens end of the projection optical system 54 from being deviated from the effective aperture of the projection optical system 54 and cannot be received by the lens end. It is possible to improve.

  Therefore, in the projector 50, a combination of the telecentric illumination optical system 52 and the non-telecentric projection optical system 54 enlarges a bright image on the projection surface with a wide angle of view even with a high performance and compact size and a large aperture ratio. Projection is possible, and the entire apparatus can be reduced in size and thickness.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

  In this embodiment, a projector having the same configuration as the DLP projector 50 shown in FIG. 1 was manufactured as an image projection apparatus to which the present invention was applied, and the light utilization efficiency was measured.

Specifically, the design data of the illumination optical system shown in the present embodiment is as shown in Table 1 below.
“Surface number i (i represents a natural number)” in Table 1 indicates that the lens surface of the lens located closest to the DMD among the lenses constituting the illumination optical system is the first, and that of the rod integrator. The numbers of lens surfaces that sequentially increase to the exit surface are shown. In Table 1, “R” indicates the radius of curvature [mm] of the lens surface corresponding to each surface number (however, a surface having a value of 0 indicates that the surface is a plane). , “D” indicates the axial distance [mm] between the i-th lens surface and the i + 1-th lens surface from the DMD side, “Nd” indicates the refractive index of each lens, and “Vd” indicates the Abbe number of each lens. ing.

Further, the design data of the projection optical system shown in the present embodiment is as shown in Table 2 below.
“Surface number i (i represents a natural number)” in Table 2 indicates that the lens surface of the lens closest to the screen among the lenses constituting the projection optical system is the first lens surface and is on the DMD side. The number of the lens surface which increases sequentially as it goes is shown. In Table 2, “R” indicates the radius of curvature [mm] of the lens surface corresponding to each surface number (however, a surface having a value of 0 indicates that the surface is a plane). , “D” indicates the axial distance [mm] between the i-th lens surface and the i + 1-th lens surface from the screen side, “Nd” indicates the refractive index of each lens, and “Vd” indicates the Abbe number of each lens. ing.

The conditions of the projector shown in the present embodiment are as follows.
Exit pupil position of illumination optics = ∞ (Telecentric)
Exit pupil position of projection optical system = 42.7 mm
Fno = 1.8
α = 8.5 °
β = 11.1 °
EFL = 23mm
BF = 22.9mm
θ1 = 12.8 °
θ2 = 3.4 °
θ3 = 2.6 °
B = 2.7

  The projector shown in this embodiment satisfies the conditions of the present invention. Then, when the light utilization efficiency of this projector was measured, the light utilization efficiency of about 81% was realized on the screen.

It is a perspective view which shows one structural example of the image projector to which this invention is applied. It is a schematic diagram for demonstrating the conditions of this invention. 3A is a schematic diagram showing a case where the exit pupil position of the illumination optical system is ∞ (telecentric), and FIG. 3B shows a case where the exit pupil position of the illumination optical system is finite (non-telecentric). It is a schematic diagram. It is a schematic diagram for demonstrating the conditions of this invention. FIG. 5A is a side view of the rod integrator, and FIG. 5B is a cross-sectional view of the rod integrator. FIG. 6A is a measurement diagram showing the shape of illumination light condensed on the DMD when the cross section of the rod integrator is a parallelogram, and FIG. 6B is a cross section of the rod integrator. It is a measurement figure which shows the shape of the illumination light condensed on DMD in the case. FIG. 7A is a schematic diagram showing a case where the exit surface of the rod integrator is cut obliquely, and FIG. 7B is a schematic diagram showing a case where the exit surface of the rod integrator is cut vertically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 50 ... Projector (image projection apparatus) 51 ... Lamp (light source) 52 ... Illumination optical system 53 ... DMD (reflection type spatial light modulation element) 54 ... Projection optical system 55 ... Screen (projection surface) 56 ... Color wheel (rotation filter) 57 ... Rod integrator (light guide member) 57 ... Aperture

Claims (5)

A light source;
A telecentric illumination optical system that collects light emitted from the light source to form illumination light; and
A reflective spatial light modulator that forms an image according to an image signal by modulating and reflecting the illumination light; and
A non-telecentric projection optical system that magnifies and projects the image onto a projection surface,
The cone angle of the illumination light reflected by the spatial modulation element is less than or equal to the cone angle of the projection optical system;
The F number of the projection optical system is Fno, the angle between the principal ray of the illumination light reflected by the spatial modulation element and the optical axis of the projection optical system is α, and the cone of illumination light reflected by the spatial modulation element When the angle is β,
Fno <1.8,
8.5 ° <α <10.5 °,
β <11.5 °
Satisfied with the relationship
EXP is the exit pupil position of the projection optical system, and θ _{1 is} the angle between the line connecting the exit pupil center of the projection optical system and the maximum image height of the spatial modulation element and the optical axis of the projection optical system, The angle formed by the lower light beam at the maximum image height of the projection optical system and the optical axis of the projection optical system is θ ₂ , the lower light beam of the illumination light reflected by the spatial modulation element, and the optical axis of the projection optical system the angle of when and θ _3,
θ ₁ = θ ₂ −sin (1 / (Fno × 2)),
θ ₂ > β−θ ₃ ,
41mm <EXP <60mm
An image projector characterized by satisfying the above relationship. When the optical magnification of the illumination optical system is B,
B> 2.6
The image projection apparatus according to claim 1, wherein the relationship is satisfied. When the back focus of the projection optical system is BF in terms of air and the focal length is EFL,
BF> EFL × 0.9
The image projection apparatus according to claim 1, wherein the relationship is satisfied. A rotary filter that is rotationally driven by disposing a color filter that separates light emitted from the light source into a plurality of color lights having different wavelengths between the light source and the illumination optical system; and A light guide member that guides the color light that has passed through each filter to the illumination optical system is disposed,
The image projection device according to any one of claims 1 to 3, wherein the light guide member has a parallelogram shape in cross-section in a direction perpendicular to the optical axis.   The image projection apparatus according to claim 4, wherein an end face on an emission side of the light guide member has a shape cut obliquely with respect to an optical axis.

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